1. Field of the Invention
The present invention relates to an electrode for continuously stimulating a facial nerve root and an apparatus for monitoring electromyograms of facial muscles using the electrode thereof.
2. Description of Related Art
A facial nerve is one of the twelve cranial nerves, called the seventh cranial nerve. The facial nerve regulates movements of “facial muscles” which make facial expressions. Muscles covering a face are regulated by a thick nerve, that is, the facial nerve.
FIG. 13 is an enlarged diagram showing the facial nerve which branches into four leading to human facial muscles. As shown in FIG. 13, the facial nerve H extending from a facial nucleus G in a brain, comes out of an inside of a right ear, and reaches facial muscles such as an orbicularis oculi muscle J around a right eye and an orbicularis oris muscle K around a right mouth.
FIG. 14 is an enlarged diagram showing the facial nerve H of FIG. 13. As shown in FIG. 14, it is observed that nerve fibers of the facial nerve H arise from the facial nucleus G, and pass behind a neighboring auditory nerve L. The facial nerve H comprises a facial nerve H1 located inside a brainstem, a facial nerve root H2 which is a root of the facial nerve coming out of the brainstem, a facial nerve H3 located in a cerebral cistern, and a facial nerve H4 located in a temporal bone as shown in FIG. 14.
FIG. 15 is a perspective view showing a conventional bell shaped electrode described in a non-patent document. M. Kohno and M. Taniguchi, “Intraoperative facial nerve monitoring during removal of acoustic neuromas and other cerebellopontine angle tumors”, Clinical Electroencephalography, 50 (8), 449-454, 2008/8. FIG. 16 is a diagram showing a state that the conventional bell shaped electrode is placed in a lesion part.
As shown in FIG. 15, the conventional bell shaped electrode 16 is formed spherical, including an upper portion which has a bell type shape, and a lower portion which is formed as a hemispherical contact portion. Here, FIG. 16 shows a state that the bell shaped electrode 16 is placed at a starting part of the facial nerve so as to contact to the starting part thereof and continuously stimulate the facial nerve at a frequency of 1 Hz.
Herein, there is a problem that it is difficult to stably hold the electrode 16 only by dwelling it on the facial nerve because the electrode 16 is formed spherical having a bell type shape. Further, since the bell shaped electrode 16 is prone to be moved when a minute force is applied to a lead wire (electrical cord), there is a problem that it is difficult to continuously stimulate a definite region of the facial nerve.
Further, there is another problem that it is difficult to stably hold the conventional bell shaped electrode as being adhesive to the facial nerve. The electrode 16 is prone to move and a stimulating position easily shifts.
For these reasons, there is a need for an electrode for continuously stimulating a facial nerve which is capable of more surely stimulating and monitoring the facial nerve than conventional electrodes, and a monitoring apparatus using the electrode thereof.